Hydrodynamically loaded web press with slipper bearing shoes

ABSTRACT

A press mechanism for removing liquid from a traveling fibrous web such as a web of paper received from the fourdrinier section of a paper machine including a backing roll and a looped traveling belt forming a press nip with the roll with a plurality of shaped shoes extending the length of the roll and pressing the belt toward the pin with said shoes having concave curved surface facing the belt and being pivotally supported so that a wedge of lubricating fluid builds up between each of the shoes and the belt to lubricate the shoes and to press the belt toward the nip. Means are provided for individually controlling the force with which the shoes are pressed toward the belt.

Jan. 1,1974 E. J. JUSTUS 3,783,097

HYDRQDYNAMICALLY-LOADED WEB PRESS WITH SLIPPER BEARING SHOES Filed May30, 1972 'United States Eatent O 3,783,097 HYDRODYNAMICALLY LOADED WEBPRESS WITH SLIPPER BEARWG SHOES Edgar J. Justus, Beloit, Wis, assignorto Beloit Corporation, Beloit, Wis.

Filed May 30, 1972, Ser. No. 258,103 Int. Cl. D215 3/06 U.S. Cl. 162-358Claims ABSTRACT OF THE DISCLOSURE A press mechanism for removing liquidfrom a traveling fibrous web such as a web of paper received from thefourdrinier section of a paper machine including a backing roll and alooped traveling belt forming a press nip with the roll with a pluralityof shaped shoes extending the length of the roll and pressing the belttoward the nip with said shoes having a concave curved surface facingthe belt and being pivotally supported so that a wedge of lubricatingfluid builds up between each of the shoes and the belt to lubricate theshoes and to press the belt toward the nip. Means are provided forindividually controlling the force with which the shoes are pressedtoward the belt.

BACKGROUND OF THE INVENTION The invention relates to an improvedextended nip press and more particularly to a pressing mechanism forextracting water from a traveling web which requires considerably lessspace and is capable of extracting more water from the web than has beenheretofore possible with conventional press couples.

The present invention provides a pressing arrangement having a pluralityof nips wherein the residence time of the web in the nips is increasedover that of a roll couple and wherein a mechanically more compactstructure is used. Attempts have been made to provide presses whichprovide for a greater pressing time and reduce the space required by thepress, but a number of these have encountered disadvantages, and thepresent structure provides advantages over structures heretoforeavailable.

As will be appreciated from the teachings of the disclosure, thefeatures of the invention may be employed in the dewatering of otherforms of webs than a paper web in a paper making machine. However, forconvenience, a preferred embodiment of the invention will be describedin the environment of a paper making machine which conventionally formsa web by depositing a slurry of pulp fibers on a traveling fourdrinierwire, transfers the web to a press section where the web passes througha number of press nips formed between roll couples, and the web thenpasses over a series of heated dryer drums and usually through acalender and then is wound on the roll. The present structure forms theentire press section and takes the place of other forms of presssections heretofore available. Modifications can be made in the overallmachine, as to the forming section, or the dryer section which can beaccommodated by the instant invention. The structure of the instantdisclosure also may be employed in pressing webs of various syntheticfibers.

The present invention relates to improvements for the press sections ofa paper making machine. Because of various inherent limitations in theoperation of roll couples forming press nips for the press section in aconventional paper making machine, only a given amount of water can beremoved in each nip and, therefore, in a conventional paper makingmachine, a series of nips are usually employed. It has been foundimpractical to attempt to remove a significant amount of additionalwater by increasing the number of press nips, although the furtherremoval of water by pressing can greatly reduce the expense and size ofthe dryer section. It is estimated that if the water removed in thepress section can be increased to decrease the moisture from 60 percentto 50 percent, the length of the dryer section can be reduced by /3.This is significant in a typical 3000 feet per minute newsprint machinewhich employs on the order of dryer drums. This significance can beappreciated in considering that the dryer drums are each expensive toconstruct and to operate and require the provision of steam fittings anda supply of steam for each drum. The relative importance of the removalof water in the press section is further highlighted by the fact thatone of the most important economic considerations in justifying asatisfactory return on investment in the operation of a paper makingmachine is to obtain the highest speed possible consistent with goodpaper formation and better pressing will shorten the necessary time inthe dryer section and permit higher speeds.

It is accordingly an object of the present invention to provide animprovement in the press section of a paper machine which makes itpossible toremove an increased amount of Water in this press section andmakes it possible to provide a press section having a relatively compactor shortened pressing area of a unique elongated or extended naturewhich does not have the performance limitations of conventional rollcouple presses and which requires far less space in terms ofrequirements as to the overall length of the press section. Byincreasing the amount of water removed from the web in the presssection, increased speeds are possible with existing equipment, i.e., agiven length of dryer section can operate at higher speeds since it isrequired to remove less water. Also, new equipment can be constructedrequiring less machine length and expense.

It is an object of the present invention to provide a press using atraveling belt wherein an improved structure is employed for applyingthe nip loading pressure to the belt.

A further object of the invention is to provide an im proved pressingmechanism for a press which counteracts the disadvantageous effects offriction and provides a press which has a uniquely long operating life.

Another object of the invention is to provide a press mechanism whereinpressures at stages along the nip are more easily controlled than instructures heretofore available.

Another object of the invention is to provide a press which avoids thedisadvantages of excessive leakage and the difficulty of providing largesliding seals as contrasted with prior art liquid pressure presses.

Other objects, advantages and features will become more apparent withthe disclosure of the principles of the invention and as will be seen,equivalent structures and methods may be employed within the principlesand scope of the invention as taught in connection with the descriptionand disclosure of the specification, claims and drawings, in which:

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view shown insomewhat schematic form of a structure embodying the principles of thepresent invention; and

FIG. 2 is a fragmentary sectional view taken substantially along lineIIII of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As illustrated in FIG. 1, abacking roll 9 is wrapped with a looped belt 10 to form an extendedpressing nip. In operation, a continuous traveling web W is passedthrough the nip along with a felt F for receiving liquid 3 pressed fromthe web. The belt is carried on rolls 11, 12, 13 and 14.

Pressure in the nip is obtained from a series of sliding shoes 16, 17and 18 which may be termed slipper bearing shoes and which have a smoothlower surface extending across the belt coextensive therewith with thesurface also extending in the direction of the belt travel to applypressure to the belt which pressure is transmitted to the web. Each ofthe shoes 16, 17 and 18 have a concave arcuately shaped lower surfacewith a relieved leading edge so as to form a wedge of lubricating fluidbetween them and the belt. For providing this lubricating fluid, asupply line 19 is provided to keep fluid within a housing 20 which hassliding seals against the belt to prevent the escape of lubricant whichcould result in the contamination of the web. Each of the shoes shouldhave a radius of approximately the same as the roll and should be curvedin such a direction so as to fit the roll. An objective is to get asmuch length of pressure as possible to form an extended pressing nip ateach of the shoes.

The shoes are pivotally supported shown at 21, 27 and 30. The shoes aresomewhat flexible over their entire length and are backed by hydraulicfluid such as so that they exert a uniform pressure against the beltalong their length thereby pressing water uniformly from the web alongthe length of the roll.

The pivotal supports 21, 27 and may be in the form of a roll pin asshown in FIG. 2 which is supported from a piston 22 in a cylinder 23containing a pressurized fluid. The piston 22 is sufficiently flexibleover its length so that with the fluid in the cylinder 23 being atuniform pressure along the length of the cylinder in accordance withPascals law, the shoe 16 will exert uniform pressure along the length ofthe roll 9. This will occur even though the downward load on the roll 9will cause downward bending thereof.

The support for each of the shoes is similar in construction and,therefore, only details for the first shoe 16 need be shown. The shoe 17has its roll pin 27 carried on a piston 28 supported in a cylinder 29.Shoe 18 has its roll pin 30 supported on a piston 31 carried in acylinder 32. Each of the cylinders are supported in an overhead supportbeam 15. This beam will also bend upwardly with a pressure in thecylinders 23, 29 and 32, but this will not affect the application ofuniform pressure by the shoes to the belt.

If a relatively wide web is expected so that it is necessary to providea long roll 9, anti-deflection means may be provided for the roll toprevent excessive bending. Such anti-deflection means may take variousforms, and in one form the roll 9 W11 be a hollow roll shell with astationary shaft extending therethrough. Fluid force transfer means willbe located between the roll shell and the shaft to transfer the loadfrom the shell to the shaft with the shaft bending downwardly relativeto the roll shell, and the roll shell maintained substantially axiallystraight. The fluid force transmission means may take various forms suchas that shown in the Justus Pat. 3,119,324.

As the web enters the nip, it is subjected first to the pressure appliedby the shoe 16, and then subsequently to the pressure supplied by theshoe 17 and thereafter by the pressure applied to the shoe 18. Largernumber of shoes may be provided. The shoes may be controlled to givesequentially increasing pressures to the web by pressurizing thechambers 23, 29 and 32 with sequentially greater pressures. In anotherform the same fluid pressure may be applied to each of the chambers, butthe chambers may be of increasing width, so that the total pres sureapplied to the web through the shoes will increase. However, in apreferred form by positioning pressure control valves 24a, 25a and 26ain the lines 24, 25, and 26 leading to the cylinders 23, 29 and 32,controlled pressures may be applied. While the shoes are preferably ofthe same length, it is contemplated that different length shoes can beemployed, such as by making the first shoe of longer length to obtain areduced unit pressure in the first zone beneath the first shoe andsuccessive increasing unit pressures in subsequent zones.

At the high speeds at which webs travel in current paper makingmachines, there is a limit to how much water can be removed at thelocation of the first shoe 16 inasmuch as hydraulic resistance pressureswill build up within the web. In other words, as the pressure is appliedvery rapidly and suddenly, the water does not have adequate time toescape if the pressure applied is too high, so that a crushing ordisturbance of the fibers will occur. Therefore, the pressure which isapplied at the first shoe 16 is predetermined at a level so that maximumwater removal will be attained without the hydraulic crushing of theweb. The pressure which is applied to the next shoe 17 can be highersince some of the water will have been removed at the first shoe.Similarly, the pressure at the third shoe 18 can be still higher. Thisprocedure is commonly followed in regular press nips where eachsubsequent nip applies a higher pressure. However, an advantage isobtained in the present arrangement in that a broader pressing area isemployed, so that the water has more time to travel from the web intothe felt. With a conventional press nip, the width of the nip isdetermined by the diameter of the press rolls, and this cannot bechanged. By increasing the length of the shoe 19, the length of timethat the web is subjected to the pressing pressure can be increased.

The present arrangement also provides an advantage over conventionalpress nip in that the pressure is applied hydraulically, that is, byvirtue of the layer of lubricating fluid which is built up between theshoe 16 and the belt 10. This lubricating liquid has a pressure profilewhich builds up from the leading edge of the shoe and then drops off atthe trailing edge of the shoe, but pressure extends along the fulllength of the shoe. This will result in improved application of pressureand improved water removal from the web as compared with the pressureprofile which occurs to a web passing through the usual two roll presscouple. Also, the need for web handling between subsequent press nips,as must be done in a conventional paper making machine employing theusual press couples, is eliminated since the web is under completecontrol from one shoe to the next. This eliminates web vibration andpossible tear and, of course, greatly reduce the space requirements of apress section.

Another modification which may be made in the structure illustrated isthat the roll 9 may be an open roll with circumferential surface groovesacross its length, or may be in the form of a suction roll. In thisarrangement the felt will be positioned against the roll and the webwill be carried on top of the felt adjacent the belt.

It is also contemplated in some constructions that a pair of parallelbelts may be employed with similar shoes positioned within the lowerbelt in opposing relation to the upper shoes. This will eliminate theneed for providing anti-deflection means for the lower roll, but becauseof the necessity of providing additional shoes and additional equipment,the illustrated arrangement is preferred.

It is further contemplated that a tension may be applied to the beltwhich will aid in the application of pressure to the web during itsentire travel through the nip. This continuing pressure between theshoes may reduce rewetting, that is, return travel of the moisture fromthe felt to the web. It also may be desirable in some installation toutilize two felts with the web sandwiched therebetween, so that one feltpasses against the belt and another felt passes against the outersurface of the roll 9. The belt 10 will travel due to its contact withthe felt and the driving forces of the roll, or in some instances, aseparate drive for the belt may be employed to drive it at substantiallythe speed of the outer surface of the roll 9.

I claim as my invention:

1. A press mechanism for removing liquid from a traveling fibrous webcomprising in combination,

a press nip formed between first and second members for receiving atraveling web therebetween,

one of said members being a traveling flexible impervious belt,

force means engaging the outer surface of said belt including a slidingshoe having a smooth surface facing the belt with said surface extendingtransversely, across the belt and also extending in the direction ofbelt travel with means for pressing the shoe toward the belt with apredetermined force,

means for providing a film of lubricating fluid between the shoe and thebelt, the leading edge of said shoe being relieved to form a hydraulicwedge of lubricating fluid between the shoe and belt,

and means for receiving liquid pressed from the Web between saidmembers.

2. A press mechanism for removing liquid from a traveling fibrous webconstructed in accordance with claim 1 and including means for pivotallysupporting said shoe about a pivotal axis extending transversely of thedirection of belt travel.

3. A press mechanism for removing liquid from a traveling fibrous webconstructed in accordance with claim 1 wherein the other of said membersis the outer surface of a rotatable roll.

4. A press mechanism for removing liquid from a traveling fibrous webconstructed in accordance with claim 1 and including a plurality ofsequentially located additional shoes in engagement with the outersurface of the belt each similarly constructed and providing additionalareas of pressure.

5. A press mechanism for removing liquid from a traveling fibrous webconstructed in accordance with claim 4 wherein each of the shoes isprovided with a pivotal support and has a relieved leading edge shapedto form a wedge of lubricant between the shoe and the belt, and thestructure includes an enclosure for retaining lubricating fluid for theshoes and enclosing said shoes.

6. A press mechanism for removing liquid from a travel ing fibrous webconstructed in accordance with claim 4 and including means forindividually controlling the force applied to each of the shoes sosequentially increasing forces can be applied to the belt.

7. A press mechanism for removing liquid from a traveling fibrous webconstructed in accordance with claim 4 wherein each of said shoes isprovided with a fluid pressure means for forcing the shoe toward thebelt.

8. A press mechanism for removing liquid from a traveling fibrous webconstructed in accordance with claim 7 wherein said fluid pressure meansincludes a piston and 6 each of the cylinders for individuallycontrolling the forces applied to the shoes to force them toward thebelt.

9. A press mechanism for removing liquid from a traveling fibrius webcomprising in combination,

a rotatable roll,

a looped flexible, impervious belt wrapped over an arc of the roll andforming a pressure nip therewith for receiving a traveling web,

a felt traveling through the nip with the web,

a plurality of slipper bearing shoes having a smooth lower surfaceextending transversely across the roll against the outer surface of thebelt,

means for delivering a lubricant between the belt and shoes,

means for pivotally supporting the shoes with said shoes being arcuatelyconcave shaped with a relieved leading edge to form a film of fluidtherebetween so that the pressure on the belt is transmitted through thewedge of fluid formed between the shoe and the elt,

and controllable fluid pressure means for pressing the shoes toward thebelt.

10. A press mechanism for removing liquid from a traveling fibrous webcomprising in combination,

a press nip formed between first and second members for reciving atraveling fibrous web therebetween,

one of said members being a traveling flexible impervious belt,

the other of said members being a cylindrical roll with the belt wrappedover an arc of the roll,

force means engaging the outer surface of said belt including a slidingshoe having a concave surface of substantially the radius of said rollextending transversely and also in the direction of belt travel withmeans for pressing the shoe toward the belt,

means for providing lubrication between the shoe and the belt,

and means for receiving liquid pressed from the web between the roll andbelt.

References Cited UNITED STATES PATENTS 2,281,860 5/1942 Renault 100-120X 3,074,764 1/ 1963 Bertelsen 100-154 X 3,293,121 12/1966 Martin 1623582,909,804 10/1959 Means 100151 UX 3,532,050 10/ 1970 Carlsmith 100-151 XROBERT L. LINDSAY, 112., Primary Examiner R. V. FISHER, AssistantExaminer US. Cl. X.R.

cylinder and a controllable fluid pressure line leads to -121, 1513152-360

